Superconductor cables contract when they are cooled to operating temperature and expand when they are heated, for example in the event of a fault. In such a situation, in particular, the end regions of the superconductor cable move in the longitudinal direction of the cable. The order of magnitude of the length change is ˜0.3%. The end regions of the superconductor are connected to normal conductors, whose other end is connected to the conductors of a so-called feed-through. Via the feed-through, the superconductor cable is connected to an electricity mains.
Especially with long cable lengths, controlling the contraction and expansion at the ends of the cables presents considerable problems.
It is known from EP 1 489 692 to connect the end of the superconductor cable to the termination of a stranded copper conductor. Contractions and expansions are thereby absorbed at the cable ends, and no forces are incurred on the statically placed termination. A disadvantage with this solution is that in the event that the superconductor cable expands, especially with long cable lengths, it is very difficult to guide the stranded conductor which is at a high voltage, and it is to be feared that the stranded conductor will enter into contact with the connection point between the superconductor cable and the housing which encloses the termination.
EP 1 617 537 A2 discloses a termination for a superconducting cable, in which the electrical conductor of the termination is electrically connected to the superconductive conductor of the cable via a tubular component made of electrically conductive material. With this solution, the conductor can slide in the component.
In a further solution to the problem, which is described in the Applicant's prior EP Application 0 529 092.4, expansion or contraction of the superconductor cable is prevented. The superconducting cable core laid in a cryostat extends inside the cryostat in the form of a corrugation or coil when the cable core is at room temperature. This is achieved by fastening a cross-like network of a material with a low thermal expansion coefficient to the cable core on particular points at longitudinal axial intervals. At operating temperature, the cable core extends substantially parallel to the cryostat, whereas at room temperature it extends in a corrugated or coiled shape. Movement of the ends of the cable core in the longitudinal axial direction is prevented by the network.